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| Titel |
Impacts of dust deposition on dissolved trace metal concentrations (Mn, Al and Fe) during a mesocosm experiment |
| VerfasserIn |
K. Wuttig, T. Wagener, M. Bressac, A. Dammshäuser, P. Streu, C. Guieu, P. L. Croot |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 4 ; Nr. 10, no. 4 (2013-04-18), S.2583-2600 |
| Datensatznummer |
250018205
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| Publikation (Nr.) |
 copernicus.org/bg-10-2583-2013.pdf |
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| Zusammenfassung |
| The deposition of atmospheric dust is the primary process supplying trace
elements abundant in crustal rocks (e.g. Al, Mn and Fe) to the surface ocean.
Upon deposition, the residence time in surface waters for each of these
elements differs according to their chemical speciation and biological
utilization. Presently, however, the chemical and physical processes
occurring after atmospheric deposition are poorly constrained, principally
because of the difficulty in following natural dust events in situ. In the
present work we examined the temporal changes in the biogeochemistry of
crustal metals (in particular Al, Mn and Fe) after an artificial dust
deposition event. The experiment was contained inside trace metal clean
mesocosms (0–12.5 m depths) deployed in the surface waters of the
northwestern Mediterranean, close to the coast of Corsica within the frame of
the DUNE project (a DUst experiment in a low Nutrient, low chlorophyll
Ecosystem). Two consecutive artificial dust deposition events, each
mimicking a wet deposition of 10 g m−2 of dust, were performed during
the course of this DUNE-2 experiment. The changes in dissolved
manganese (Mn), iron (Fe) and aluminum (Al) concentrations were followed
immediately after the seeding with dust and over the following week. The Mn,
Fe and Al inventories and loss or dissolution rates were determined. The
evolution of the inventories after the two consecutive additions of dust
showed distinct behaviors for dissolved Mn, Al and Fe. Even though the mixing
conditions differed from one seeding to the other, Mn and Al showed clear
increases directly after both seedings due to dissolution processes. Three
days after the dust additions, Al concentrations decreased as a consequence
of scavenging on sinking particles. Al appeared to be highly affected by the
concentrations of biogenic particles, with an order of magnitude difference
in its loss rates related to the increase of biomass after the addition of
dust. In the case of dissolved Fe, it appears that the first dust addition
resulted in a decrease as it was scavenged by sinking dust particles, whereas
the second seeding induced dissolution of Fe from the dust particles due to
the excess Fe binding ligand concentrations present at that time. This
difference, which might be related to a change in Fe binding ligand
concentration in the mesocosms, highlights the complex processes that control
the solubility of Fe. Based on the inventories at the mesocosm scale, the
estimations of the fractional solubility of metals from dust particles in
seawater were 1.44 ± 0.19% and 0.91 ± 0.83% for Al and
41 ± 9% and 27 ± 19% for Mn for the first and the second dust
addition. These values are in good agreement with laboratory-based estimates.
For Fe no fractional solubility was obtained after the first seeding, but
0.12 ± 0.03% was estimated after the second seeding. Overall, the
trace metal dataset presented here makes a significant contribution to
enhancing our knowledge on the processes influencing trace metal
release from Saharan dust and the subsequent processes of bio-uptake and
scavenging in a low nutrient, low chlorophyll area. |
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